When you turn on the M100 does the screen come on all black? The way the LCD controllers work is that they will turn 'ON" every LCD segment upon power up. When the M100 boots it will send a 'clear' signal to the LCD controllers. If you don't see the solid black screen it is an indication of a power supply issue.
As Fugu said check the -5V, +5V to the LCD I would check on the LCD side of the connector first. If you don't have both supplies, then trace it back to the source. Jeff From: M100 <[email protected]> On Behalf Of Fugu ME100 Sent: Saturday, July 21, 2018 4:31 PM To: [email protected] Subject: Re: [M100] Model 100 LCD doesn't work You may have already checked but make sure the -5V is good and that the contrast pot is working sometimes they do not work so the screen is in low contrast mode = not visible but still working. You should be able to see the screen go almost entirely black as you turn the contrast pot or the menu might appear :) Buzz out all the connections to the LCD header make sure no other trace has been damaged by a capacitor leak, it is possible to miss a break. Make sure the connection onto the LCD is good and no corrosion has happened due to capacitors out gassing. I have had a trace corrode under one of the caps that caused the screen to stop working. The fact it beeps is a good sign it means the keyboard interface seems to be working, some of the same chips drive the LCD so they are probably good.
